NTSR1 glycosylation and MMP dependent cleavage generate three distinct forms of the protein

Abstract

NTSR1 abnormal expression by cancer cells makes it a strategic target for antitumoral therapies, such as compounds that use NTSR1 binding probes to deliver cytotoxic agents to tumor cells. Success of these therapies relies on NTSR1 protein availability and accessibility; therefore, understanding the protein’s biology is crucial. We studied NTSR1 protein in exogenously and endogenously expressing non-tumoral and tumoral cells. We found NTSR1 to be expressed as three distinct protein forms: the NTSR1-high form, a glycosylated protein; the NTSR1-low form, a N-terminally cleaved and de-glycosylated protein; and the NTSR1-LP protein with the MW size predicted by its NTSR1 amino acid sequence. We show that the NTSR1-high form is cleaved by MMPs to generate the NTSR1-low form, a process that is promoted by the Neurotensin (NTS) ligand. In addition, NTS induced the internalization of plasma membrane localized NTSR1 and degradation of NTSR1-low form via the proteasome. Importantly, we found NTSR1-low form to be the most abundant form in the tumoral cells and in PDAC Patient Derived Xenograft, demonstrating its physiopathological relevance. Altogether, our work provides important technical and experimental tools as well as new crucial insights into NTSR1 protein biology that are required to develop clinically relevant NTSR1 targeting anti-tumoral therapies.

Targeting the NTSR2/TrkB oncogenic pathway in chronic lymphocytic leukemia

“…In contrast, the presence of NTSR2 was confirmed in all three conditions tested. It is worth noting that we observed two distinct bands for NTSR2, similar observations have been made for NTSR1, it was found to be expressed as three distinct protein forms, one being a glycosylated form, another being a N-terminally cleaved and de-glycosylated form, and a last one with the size predicted by its amino acid sequence 25 . Surprisingly, we also observed a slight shift in molecular weight for NTSR2 between the cell lysates and the pull-down samples.…”